Fix initialization sequence translation bug.

BUG=angle:805
TEST=https://www.khronos.org/registry/webgl/sdk/tests/conformance/glsl/misc/expression-list-in-declarator-initializer.html

Change-Id: I94fbdd0824dbe73034f8bf022aa53627582ad48b
Reviewed-on: https://chromium-review.googlesource.com/224813
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Zhenyao Mo <zmo@chromium.org>
diff --git a/src/compiler/translator/OutputGLSLBase.cpp b/src/compiler/translator/OutputGLSLBase.cpp
index 5f5e058..a295aee 100644
--- a/src/compiler/translator/OutputGLSLBase.cpp
+++ b/src/compiler/translator/OutputGLSLBase.cpp
@@ -743,7 +743,7 @@
         writeBuiltInFunctionTriplet(visit, "notEqual(", useEmulatedFunction);
         break;
       case EOpComma:
-        writeTriplet(visit, NULL, ", ", NULL);
+        writeTriplet(visit, "(", ", ", ")");
         break;
 
       case EOpMod: